Fuu Houhou, also known as Feng Baobao, is a central figure shrouded in mystery. She first appears intervening to save Chou Soran from zombies in a cemetery, instantly revealing her link to his grandfather, Zhang Xilin, whose grave was desecrated. Fuu exhibits an ageless appearance, maintaining youth despite being active since at least 1944, suggesting she has lived over a century without aging. Her origins are largely unknown due to severe amnesia; she recalls only her name and possesses no memories of her family or life before discovery. Found mute and injured in wartime China's mountains in 1944 by Jo Shou's parents, they took her in. When bandits attacked their village, killing Jo Shou's father, she lethally dispatched the attackers under his mother's plea, showing no emotion. This act terrified the villagers, leading to her ostracism and exile back to the mountains.

Fuu possesses exceptional combat abilities marked by high agility, knife proficiency, and unconventional tactics like joint dislocation to escape restraints. She weaponizes everyday objects, notably using high heels against Ja Jongu. Her physical resilience is augmented by rapid regenerative healing, enabling recovery from severe wounds, including a pierced heart, through rest. Despite her prowess, she displays limited understanding of social cues and emotions, often speaking in a detached monotone that unnerves others.

Affiliated with the covert organization "Express Delivery" (哪都通), which monitors and regulates supernatural Outsiders, she collaborates with operatives like Jo San and Jo Yon. Her primary motivation is uncovering her forgotten past, aligning with her guardianship of Soran—a promise made to his grandfather. This protective role evolves into a partnership during the Raten Tournament, where she battles and aids Soran's investigation into his family secrets. The tournament further explores her immortality; a confrontation with Ou Riken reveals a disconnection between her spirit and soul, hinting at unnatural origins for her enduring existence.

Throughout various story arcs, Fuu demonstrates autonomy in critical decisions, such as rejecting traditional Tenshi succession rites to prioritize direct truth-seeking about her and Soran's lineage. Her relationship with Soran remains pragmatic yet steadfast, focused on mutual goals despite her emotionally reserved demeanor. Her background includes fragmented associations with historical Outsider conflicts like the Koushin War and the 36 Bandits' defection to Zensei, though her exact role remains undisclosed. The narrative underscores her relentless quest for identity as the driving force across all appearances, positioning her as both guardian and an integral mystery within the series' Outsider lore.